1. Field of the Invention
This invention relates to vehicle leveling systems, and more particularly, to a new and improved vehicle leveling device incorporating a novel electronic height sensing apparatus.
2. Description of the Related Art
Vehicle leveling systems function to maintain a predetermined height relationship between a chassis (sprung portion) of a vehicle and its ground engaging axle assemblies (unsprung vehicle portion). Such systems utilize one or more auxiliary fluid suspension components to supplement the load carrying capacity of the primary vehicle springs. A pressure source is often included in such leveling systems for supplying pressurized fluid to the auxiliary suspension components when a load of predetermined magnitude has been added to the vehicle chassis. Upon such loading, the auxiliary suspension components become operable to supplement the load carrying capacity of the primary springs to return the vehicle chassis to a desired height relationship with respect to the ground engaging axle assembly. When the vehicle load is removed, the primary suspension springs and pressurized auxiliary suspension components co-act to cause the chassis to rise above the desired relationship. When this occurs, the leveling system causes the pressurized fluid to be exhausted from the auxiliary suspension components.
To accomplish the aforesaid pressurizing and exhausting of fluid from the auxiliary suspension components, it has been the practice to utilize some type of a height detecting controller. For example, U.S. Pat. No. 4,017,099 discloses an external height detecting controller located remote from vehicle leveling struts of vehicle leveling systems. Such height detecting controllers generally function to vary the attitude or trim height between the ground engaging axle of a vehicle and a vehicle's chassis. The height detecting controller senses sustained changes in the height relationship between the axle and chassis and controls fluid flow between a suitable source of a pressurized fluid and the suspension struts. Such remotely located controllers have been found to be objectionable because they often require separate factory installation. Additionally, such controllers require accurate positioning and calibration adjustment in order to assure the desired overall operation of the leveling system.
While integrated controllers and suspension struts have been proposed in the U.S. Pat. Nos. 3,584,894 and 3,606,375, such devices have been found to be objectionable due to the fact that they were located externally of the suspension struts and thus were subject to the hostile environment that exists in connection with modern automotive vehicles.
Aforementioned U.S. Pat. No. 4,017,099 discloses an arrangement by which the height controlling elements are located interiorly of the pressurizing chamber. U.S. Pat. No. 4,141,572 discloses a refinement of the principles set forth in the earlier mentioned patent by which the height sensing elements and their associated electronic circuitry may be conveniently mounted directly upon one peripheral wall portion of the pressurizing chamber of the associated leveling strut.
U.S. Pat. Nos. 4,017,099 and 4,141,572 and the present invention are preferably combined with an electrical connector arrangement. The connector is intended to be communicable via a suitable opening or aperture in the suspension strut dirt shield with suitable electrical conductors connected to the associated control system and pressurizing source. Additionally, because a portion of the associated electrical circuitry and height sensing means are supported within the pressurizing chamber, they are protected from the hostile exterior environment. However, aforementioned U.S. Pat. Nos. 4,017,099 and 4,141,572 disclose height sensing control mechanisms utilizing optical height sensing means including a light source and means sensitive to the light source for controlling pressurization of the vehicle leveling strut. Specifically, a pair of light sensitive devices are mounted substantially opposite from a light source upon the interior wall of the dirt shield, or to a support member secured thereto, and are operatively associated such that when the reciprocating shock absorber cylinder blocks the transmission of light from the light source to one or both of the light sensitive devices, an electrical signal is produced to actuate the source of fluid pressure so as to adjust the leveling strut height accordingly. Pre-assembly alignment of the light sensitive devices with the light source so as to direct sufficient light transmission is required.
Further methods for sensing the variable location of reciprocating components are disclosed in United Kingdom patent application No. GB 2 163 260 A, as well as U.S. Pat. Nos. 4,502,006 and 4,623,840. These patents disclose methods and apparatuses for sensing the real-time variable position of a reciprocating member. These references are adapted for variable displacement sensing rather than to discrete positional sensing to which the present invention is directed.
It is to be noted that the terms "height," "distance," "attitude," etc. and derivatives thereof are used interchangeably herein as well as throughout the automotive art, as referring to the magnitude of spacing between a vehicles sprung and unsprung portions (e.g., between a vehicle frame and its associated axles). It is also to be noted that the term "associated electronic circuitry" used herein is intended to mean wires, conductors (either discrete wires or printed circuits), as well as electronic components per se, either solid state or otherwise or any combinations thereof. Lastly, the vehicle leveling device described herein which incorporates the novel electronic height sensing apparatus encompasses application to either suspension "struts" or "shock absorbers" as utilized in vehicle leveling systems.